Abstract: Requirements specification is a collaborative
activity that involves several developers specifying the
requirements elicited through several stakeholders.
Operation-base merging allows combining specifications
using the information available about their state as well
as their evolution or change. Thus, leading to a more
precise, accurate and efficient merging. Differencing
specifications is a tedious, complicated, and a crucial
process needed for operation-based merging of
specifications resulting from collaboration. An approach
for differencing Object-Oriented formal specifications is
proposed in this paper. The difference is modeled as a set
of primitive operations and is produced based on the
matching results of specifications' elements. These
matchings are calculated based on an approach employing
elements' syntactic and structural similarities. The
proposed differencing approach is empirically
validated.